Problem: Solve for $x$ and $y$ using substitution. ${3x-6y = 3}$ ${x = 6y+5}$
Solution: Since $x$ has already been solved for, substitute $6y+5$ for $x$ in the first equation. ${3}{(6y+5)}{- 6y = 3}$ Simplify and solve for $y$ $18y+15 - 6y = 3$ $12y+15 = 3$ $12y+15{-15} = 3{-15}$ $12y = -12$ $\dfrac{12y}{{12}} = \dfrac{-12}{{12}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = 6y+5}\thinspace$ to find $x$ ${x = 6}{(-1)}{ + 5}$ $x = -6 + 5$ ${x = -1}$ You can also plug ${y = -1}$ into $\thinspace {3x-6y = 3}\thinspace$ and get the same answer for $x$ : ${3x - 6}{(-1)}{= 3}$ ${x = -1}$